[ASK] Attenuator bandwidth range, does bigger always better ?

[BravoV]

I've asked same question -> HERE, but no answer yet, so I think maybe I will get it here.

It's about getting an attenuator for my spectrum analyzer to prevent overloading the input.

My SA input range is 9KHz-3GHz, should I buy the one say capable of DC-3GHz, or the higher the better say like DC-10GHz or even DC-20GHz ? Or any other comments or suggestions ?

Thanks in advance.

[Neganur]

Worst thing to happen is that it's not attenuating "well" beyond its rated bandwidth.

That could mean that if the signal you're sending though it has a strong 2nd or 3rd harmonic and some parts of the signal chain somehow manage to have mixing products that fall into the DC-3GHz range of your SA, then you may see some spur.

I don't think this will be significant enough to worry about it, the power of the harmonics will be less than the fundamental in any case.

[BravoV]

Neganur, thanks for replying ! 

Worst thing to happen is that it's not attenuating "well" beyond its rated bandwidth.

That could mean that if the signal you're sending though it has a strong 2nd or 3rd harmonic and some parts of the signal chain somehow manage to have mixing products that fall into the DC-3GHz range of your SA, then you may see some spur.

Noted, especially on the possible spurious signal beyond my SA's range.

Which is pointless right ? CMIIW

I don't think this will be significant enough to worry about it, the power of the harmonics will be less than the fundamental in any case.

Actually I'm planning to use it with my old time mark generator, as a comb generator as it generates really narrow sharp pulse, in order to see it's harmonics and it's linearity at my SA as its used one, will this matter ?

[Karlo_Moharic]

Just use the one that matches your SA bandwith and that's it

[TheSteve]

What are the chances you'll eventually get another analyzer with a higher top frequency? It would be nice to keep using the same attenuators.

[BravoV]

What are the chances you'll eventually get another analyzer with a higher top frequency? It would be nice to keep using the same attenuators.

Pretty slim chance. Guess I will stick to 3GHz or at least near it, thanks.

[eb4fbz]

The bigger the better. Attenuators bandwidth is usually specified by their return loss bandwidth instead of the att flatness. Attenuation flatness is better on precission attenuators, and ir ripples when the RL is degraded.

[BravoV]

Still in context of protecting SA input, how about the DC Block adapter low range ? As most I've noted starting from 10 MHz.

[Neganur]

That means that the block you're looking at does not have any significant insertion loss after 10 MHz.
It's a cap after all, think of how large a cap must be to not pose much resistance (reactance) at 9 kHz

You probably have blocking caps in circuits at below 10 MHz anyway, or what is it that you want to measure?

[BravoV]

That means that the block you're looking at does not have any significant insertion loss after 10 MHz.
It's a cap after all, think of how large a cap must be to not pose much resistance (reactance) at 9 kHz

You probably have blocking caps in circuits at below 10 MHz anyway, or what is it that you want to measure?

Yeah, what strange is I just purchased an used one that is 9KHz-8GHz, a Rosenberger brand, weird isn't it ? 
Its still on it's way here, and attached photo from the seller.

Edit :
Some spec on this DC Block from Rosenberger

Return loss
>= 25 dB, 9 KHz to 1 GHz
>= 18 dB, 1 GHz to 4 GHz
>= 15 dB, 4 GHz to 8 GHz

Insertion loss
<= 1.10 dB, 9 KHz to 8 GHz

Is this decent ?

[tautech]

Yeah, what strange is I just purchased an used one that is 9KHz-8GHz, a Rosenberger brand, weird isn't it ? 
Its still on it's way here, and attached photo from the seller.

Brave Bravo, first steps into the RF rabbit hole. 

Brave bunny Bravo or Bravo brave bunny.......................never mind. 

[BravoV]

LOL .. stop provoking me  , as I'm already deeply infected by TEA.   

As the SA without a TG, pretty sure you already can guess what is next subsequently ... 

Still, feeling noob and much to learn.

[BravoV]

Does Midwest Microwave brand fixed attenuator considered a good one ?